N1201SA Antenna Analyser Review 

Yep - and then, there is the story of the bad antenna at the other end of the lossy cable. Since the cable ate most of the energy going up to the antenna, and once again ate most of the power reflected back, the SWR meter at the transmitter end received little reflected power, and indicated all fine.

JD FPV great vid How do you check the strength of a signal?

+caliphaxable it will do anything you hook up, however the transmission line will cause some skew in the readings. At that Freq and over those distances it should be negligible unless the line is really bad.

I have had some success using a sdr on my computer and comparing the signal strength received from a dipole as my reference and comparing it to that of the test antenna. you could use he test antenna for receive or transmit. In my case i compared against a dipole in whatever case i would use it for. (send or receive) and leave the same antenna on the other end.

seems to be i've been using it on all the antennas i own, even commercial ones for HAM which I have also tested with the Rigexpert and i get very comparable results at least at the low end.

I bought an adapter kit from banggood which pretty much converts everything to everything. I use this little $1 adapter on my radios a lot www.banggood.com/RPSMA-Female-to-RPSMA-Female-Adapter-RF-Connector-RPSMAKK-p-925208.html?p=DU052212075452015025 The version I have connects with standard SMA, not sure why you'd want to buy one with such an uncommon connector.

S11 tells you how much power sent out by the VNA comes back. So first, connect your coax to the VNA. Connect nothing at the other end (leave the coax open, not shorted). The S11 value then tells you the dB loss of a *two* way trip through the coax at a given frequency. Use the graph screen to see loss over a frequency range. So maybe you are using a 440 MHz antenna, so set the VNA test frequency and connect your coax to the VNA only. So maybe it displays S11: -3 dB; then your coax run loses 1.5 dB *one* way at 440 MHz. So on coax alone, higher S11 (like -1 dB instead of -10 db) is better. Then connect the antenna to the coax. Maybe now the VNA displays S11: -15 dB. So 1/32 of the power from the VNA came back. But 3 dB was lost in the coax alone (see above). So -12 dB (1/16 of the power that reached the antenna) came back instead of being radiated, which is not bad. So lower adjusted S11 (the -12 dB above) is better. Higher adjusted S11 means the antenna is not tuned for the frequency or is not impedance matched to the coax. So low S11 because your coax is lossy = bad. Low S11 because your antenna radiated almost all of the power = good. Note: "Low S11" means more negative (-15 dB is lower than -3 dB) Z is the impedance that the VNA sees. It is not the impedance of your antenna if you have a long coax run connected or a matching network. Connect the antenna's RF connector directly to the VNA or use a short coax jumper to see true antenna impedance. Z should normally be close to 50, as that is what your radio and coax want to see. Numbers close to 50 (maybe 40 to 60?) are not that bad. Other numbers mean your antenna (or antenna plus matching network) is not tuned or has a design problem or is damaged. X is reactance (capacitive or inductive) and should be near zero. As you move away from zero, it shows that there are problems. Reactance means there will be RF power that the antenna will not radiate, i.e. an efficiency loss. -5 to +5 is quite good; up to -20 to 20 is probably ok. And no, a VNA can not calculate antenna gain. There is nothing being sent over the coax that can tell the VNA that.

Thanks alot. This helped so much.. Btw, im trying to make a great 2.3 to 2.6ghz multirange antenna. here are the results, "" R 54 X18 vswr 1.4 and s11 -15 ""will it blend ?

On my multiple tests, i see when an antenna is multirange, it has a low power. A single channel antenna always has better values and a peak at S11 am i right ?

R 54 is good. X 18 is ok. You did not report Z. VSWR 1.4 is probably because the antenna is wide (not single frequency), so is to be expected. S11 reading is hard to say unless you know how much power is lost in the coax. If the coax is very short, then you can guess that is does not lose much (maybe a few dB), so then you are looking at maybe -13 dB for power bouncing back from the antenna, so the antenna is only kicking back about 1/20th or less of the power and you should be ok with that...

i calculate the loss, its -0.9 (S11dB) coax is very short. And the Z is 49